Typically, service providers deliver media streams including video data in one of three forms: broadcast, multicast or unicast. According to the traditional broadcast model, a provider sends the same video content to all transceivers serviced by the provider. In a multicast system, a provider sends the same multicast stream to a service group, a subset of subscribers that are commonly served by a network node or group of nodes. All subscribers in the service group viewing the same multicast program receive and share the same multicast video stream. In contrast to broadcast stream delivery, multicast stream delivery offers a limited opportunity for content stream alteration at the service group level. For example, advertisements sent to subscribers of a service group sharing a multicast stream can be catered to a demographic profile of the subscribers in the service group. In a unicast system, a provider sends a separate unicast stream to each single subscriber endpoint (e.g., a transceiver such as a set-top box (STB)). Every unicast stream sent to a subscriber is unique; that is, even if different subscribers are viewing the same program, each subscriber receives and decodes a separate unicast video stream, thus significantly increasing the total bandwidth required to transmit the video program to all unicast subscribers relative to broadcast and multicast delivery methods. However, unicast stream delivery offers an opportunity for video stream content personalization on an individual subscriber level.
Switched digital video is a network scheme for distributing digital video via a network channel having limited bandwidth capacity. The term switched digital video applies to digital video distribution on typical cable television systems using quadrature amplitude modulation as well as to systems utilizing Internet Protocol. The initiative behind switched digital video is that video service providers do not send unwatched programs over the network, thus permitting a more efficient use of bandwidth.